The present invention relates generally to clutches and, in particular, to electric control circuits for electro-magnetically actuated clutches.
In order to overcome high spring and/or initial loading and to obtain rapid actuation of an electromagnetic clutch, it is common to generate a magnetic force which is substantially greater than the force required to maintain the clutch in the actuated state. The greater magnetic force is generated by over-energizing an associated electromagnetic coil for a relatively short period of time so that the coil is not damaged. One method to achieve such operation is to provide two different coils which differ in the number of winding turns. The coils are wound such that their magnetic fields reinforce each when both are energized. In a starting mode, an electronic circuit connects the coils in parallel to the power source for an improved speed of response. After a predetermined time, the coils are connected in series to the same power source for operation in a run mode.